One type of closed loop solar collection system known in the prior art includes a concentrating cylindrical parabolic reflector focusing solar energy on a linear vaporizer tube aligned along the focal line of the reflector. A quantity of vaporizable heat transfer or working fluid, such as water, is vaporized within the tube and flows out one end through a pipe to drive a steam engine, turbine or other device. In a steam engine, for example, vaporized fluid drives a piston to deliver power for a variety of applications, e.g., pumping water for irrigation. After the working fluid drives the piston through a stroke, spent low enthalpy vaporized fluid is discharged through a series of discharge ports provided within the cylinder of the engine. The fluid flows from the discharge ports through a pipe into a condensor, where heat from the vaporized fluid is extracted, condensing the fluid. The condensed fluid is then pumped to a storage tank to resupply the receiver.
In conventional closed loop solar collection designs of which I am aware, electrically operated servo-type valves are used to control the engine intake valves to maximize engine efficiency However, since this type of electronic steam injection technique requires an outside source of electrical power, it is impractical at remote or wilderness sites. On the other hand, manually operated valve mechanisms to control engine speed require sophisticated valve linkages to maximize engine efficiency by tailoring valve operation to variations in engine load.
Another problem associated with various closed loop solar collector systems is in utilizing an electrically driven circulation pump to control the flow of condensed fluid from the supply tank into the receiver. Apart from requiring an outside source of electrical power to operate such auxiliary pumps, frequent maintenance is often necessary in rugged and hostile environments, such as at remote or wilderness sites. If the pump fails, insufficient fluid is released into the receiver tube, allowing the tube to run dry and thereby to overheat.
It is accordingly an object of the present invention to provide a closed loop linear concentrating solar collecting system having improved means for regulating the flow of a heat transfer or working fluid through the system.
Another object is to provide a closed loop concentrating solar collector system having an automatic fluid circulating means which requires no source of power, other than the sun, for operation, and which is capable of controlling the level of working fluid in a fluid receiver or boiler.
A further object is to provide a system that is simple to construct and reliable in rugged and hostile environments with minimal supervision and maintenance.
Still another object is to provide a circulatory system that is capable of operating continuously and reliably for long periods of time.
Still a further object is to provide a steam engine having improved means for controlling engine operation under a wide range of receiver tube pressures for efficient power delivery.
Yet a further object is to provide a steam driven engine that is automatically self-starting and requires no manual adjustment or intervention to maximize engine operating efficiency.